From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Sources of radio interference from engine components and methods for suppression.
| Identifier | ExFiles\Box 168b\1\ img273 | |
| Date | 6th May 1938 guessed | |
| RADIO DEVELOPMENT. 6153 file 2 Oct. ENGINE INTERFERENCE. The main source of interference is generally due to the contacts on the regulator coil. This was proved by inserting a strip of insulating material between the contacts and running the dynamo at approx. 4000 R.P.M. thus counteracting the resistance that was automatically connected into the circuit when the contacts were opened, and letting the dynamo charge at its normal rate. A more accurate measure was adopted by disconnecting the coil and inserting a variable resistance in its place so that the charging current could be regulated as the engine either increased or decreased its speed. In both cases the interference from that source was nil. There is also another possible source of interference and that is due to radiation along the dynamo leads of H.F. currents generated by the contacts as the engine varies its speed. This was improved by running screened cable from the dynamo and regulator and also by placing an earthed metal screen over the regulator itself. All this interference is introduced into the receiver from the aerial and the most effective method of eliminating it is by using a roof aerial which, by virtue of its position is well clear of all electric fields radiated from the regulator or its wiring. The dynamo itself always needs a condensor connected from one of its terminals to earth, generally the tie is the most satisfactory. Condensers were tried at various points on the regulator system and with the exception of the dynamo they made no improvement. Ignition interference is nearly always cured by fitting a suppressor in the main distributor lead, sometimes an additional condenser has to be fitted from the battery or switch terminal of the coil to earth. The rest of the electric equipment causes no interference, but sometimes interference is obtained from petrol pumps, windscreen wipers, etc. but as a rule they are of no account; as regards this interference a great deal depends upon the make and design of the receiver fitted, - most good makes of receivers have incorporated suppressors and the result of this is that this equipment causes very little trouble. Continued. | ||